IGRT PLANNING PROCEDURE|
Immediately after the diagnosis, it is necessary to discuss the treatment options with cancer specialists, such as a surgeon, a medical oncologist and a radiation oncologist, through the primary care physician. These specialists work together as a team, and recommend the treatment. In many cases, cancer needs to be treated by using more than one type of treatment. For example, for breast cancer, a patient might have to undergo surgery for the removal of tumour (by a surgeon), then have the radiation therapy to destroy any remaining invisible cancer cells in or near the breast (by a radiation oncologist) and may also have to receive chemotherapy (by a medical oncologist) which destroy cancer cells that have travelled to the other parts of the body.
Following are the Steps of Radiation Therapy Procedure
Step 1: Immobilisation
To deliver therapy precisely, the patient has to be kept exactly in the same position every day. For this and to prevent movement of the patient during the treatment proper immobilization is the most essential component of modern day radiotherapy. The patient and the site of the disease are examined carefully for suitability for a particular type of immobilization. Carbon fibre base-plates, thermoplastic materials, vacuum cushions, cushion managers/holders and locally engineered devices are used depending upon the requirement. Experienced technologists and physicists are involved in the process of suitable choice of immobilization along with Consultant Radiation Oncologists. A very carefully chosen immobilization is the basic requirement of a good treatment planning and delivery.
Step 2 : Imaging For Planning
After the immobilization procedure, the patient undergoes the type of imaging procedure that is required. Special treatment planning CT scan is done on every patient to help the treatment planning using a dedicated CT scanner in the department. This planning CT scan is in addition to diagnostic CT scan that would have been done earlier. This CT scan is then pushed through the network to the computer planning system. Some times MRI and PET images are requested and are overlapped over the CT scan using the fusion software to get the clear details of the tumour.
The Consultant Radiation Oncologist along with senior technologists uses the images thus obtained, in the virtual simulation software to reconstruct different views of the treatment area, volume in terms of tumour and normal tissues. The treatment directions (Gantry angle) and fields are tailored by the Consultant Radiation Oncologist. This is a very important work and involves highly scientific, clinical and labour intensive effort and may take between 1 and 3 hours.
Dosage is decided by the Consultant Radiation Oncologist. After this, the Medical Physicist calculates the Monitoring Units (MU) which is based on the intensity of the radiation from the machine and also the information about the patient, site and geometry specific data.
Step 3 : Treatment Planning
Here, sophisticated treatment-planning computer software is used to design different types of treatment plans. These plans are made by Medical Physicists, who direct and tailor the beams, as per the clinical requirements of the Consultant Radiation Oncologist. Multiple plans are generated and evaluated. The best among them is selected after detailed study and the approved plan is transferred to the treatment machine. Concurrently, patient-specific and plan-specific quality assurance (QA) checks are performed for every plan. This QA, performed by Medical Physicists, may take anywhere between 2 and 5 hours.
Step 4 : IGRT Treatment Sessions
Each session of external beam radiation is painless, a procedure similar to getting an X-ray done and is usually given in several sessions. The radiation is directed at the tumour from a machine located away from the body, using the linear accelerator. External beam radiation is non-invasive. One of the benefits of radiation therapy is that it is usually given as a series of outpatient treatments. Treatments are usually scheduled for five days a week, Monday through Friday, and may continue for 1 to 8 weeks. The number of radiation treatment depends on the size, location and type of cancer, the intent of the treatment, general health of the patient and other medications the patient may be receiving.
Preparation phase: Here the patient is set up in treatment position. Machine is moved to imaging position and the Flat Panel, which takes the CT picture, is moved into required position on the other side of the patient.
Acquisition and reconstruction of the image: The CT picture is taken and image is reconstructed and displayed on the monitor in the treatment console.
Reviewing the planning data: Planned data along with the CT images (done and stored earlier), are retrieved by the console computer and reviewed.
Automatic registration: Reconstructed CT image taken with the patient in treatment position is overlapped over the “planned CT image” done earlier and automatically co-registered by alignment of bony structures.
Manual registration: The registration can be done manually as well, if the clinician is not satisfied with auto-registration. Here, after studying the images of organs and tumours in their entire volume, the cone beam CT image is moved by the radiation oncologist/therapist for better alignment with the “planned CT image” and data.
Offset data displayed: 3 dimensional variations in position of the patient as on that day, in relation to the position as per the plan, is displayed on the monitor.
Patient repositioning: The patient is repositioned if the variation is beyond the acceptable level, e.g. variation of 3mm or beyond.
The whole procedure takes roughly about 6 minutes.
Step 5 : Port Films
During the course of treatment, correct positions of the treatment beams with reference to the volume of interest / treatment are regularly verified with images made, using the treatment beam. These images are called port films, which represent an important quality assurance check.
Protocol of doing IGRT daily or otherwise varies from clinic to clinic. Port film checking may be done alternating with IGRT depending on the protocol of that hospital.
After the treatment is completed, follow-up appointments are scheduled at regular intervals so that the Consultant Radiation Oncologist supervises the recovery and continues to monitor sequélae (side effects) and general health status. The Consultant Radiation Oncologist may also order additional diagnostic tests. Reports on treatment may also be sent to the other Specialists involved in the management of the patient.